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Title: Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface

Abstract

Two new intermolecular vibration--rotation-tunneling (VRT) bands of Ar--NH{sub 3} have been measured using tunable far infrared laser spectroscopy. We have unambiguously assigned these and a previously measured FIR band (Gwo {ital et} {ital al}., Mol. Phys. {bold 71}, 453 (1990)) as {Pi}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), {Sigma}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), and {Sigma}(0{sub 0}, {ital n}=1){l arrow}{Sigma}(0{sub 0}, {ital n}=0). The three upper states of these are found to be strongly mixed by anisotropy and Coriolis effects. A simultaneous least squares fit of all transitions has yielded vibrational frequencies, rotational and centrifugal distortion constants, and a Coriolis parameter as well as quadrupole hyperfine coupling constants for the upper states. An effective angular potential energy surface for Ar--NH{sub 3} in its lowest stretching state has been determined from these data, after explicitly accounting for the effects of bend stretch interactions. Features of the surface include a global minimum at the near T-shaped configuration ({theta}=90{degree}), a 30 cm{sup {minus}1} to 60 cm{sup {minus}1} barrier to rotation at {theta}=180{degree} (or 0{degree}), and a very low barrier or possibly a secondary minimum at {theta}=0{degree} (or 180{degree}). Both attractive and repulsive interactions are shown to contribute significantly to themore » anisotropic forces in the complex. Comparison with {ital ab} {ital initio} calculations are presented.« less

Authors:
; ; ;  [1]
  1. Department of Chemistry, University of California, and Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (USA)
Publication Date:
OSTI Identifier:
5467385
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics; (USA)
Additional Journal Information:
Journal Volume: 95:1; Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ARGON COMPLEXES; INFRARED SPECTRA; ADDUCTS; AMMONIA; ARGON; POTENTIAL ENERGY; ROTATIONAL STATES; VIBRATIONAL STATES; COMPLEXES; ELEMENTS; ENERGY; ENERGY LEVELS; EXCITED STATES; FLUIDS; GASES; HYDRIDES; HYDROGEN COMPOUNDS; NITROGEN COMPOUNDS; NITROGEN HYDRIDES; NONMETALS; RARE GASES; SPECTRA; 640302* - Atomic, Molecular & Chemical Physics- Atomic & Molecular Properties & Theory; 400102 - Chemical & Spectral Procedures

Citation Formats

Schmuttenmaer, C A, Cohen, R C, Loeser, J G, and Saykally, R J. Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface. United States: N. p., 1991. Web. doi:10.1063/1.461430.
Schmuttenmaer, C A, Cohen, R C, Loeser, J G, & Saykally, R J. Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface. United States. https://doi.org/10.1063/1.461430
Schmuttenmaer, C A, Cohen, R C, Loeser, J G, and Saykally, R J. Mon . "Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface". United States. https://doi.org/10.1063/1.461430.
@article{osti_5467385,
title = {Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface},
author = {Schmuttenmaer, C A and Cohen, R C and Loeser, J G and Saykally, R J},
abstractNote = {Two new intermolecular vibration--rotation-tunneling (VRT) bands of Ar--NH{sub 3} have been measured using tunable far infrared laser spectroscopy. We have unambiguously assigned these and a previously measured FIR band (Gwo {ital et} {ital al}., Mol. Phys. {bold 71}, 453 (1990)) as {Pi}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), {Sigma}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), and {Sigma}(0{sub 0}, {ital n}=1){l arrow}{Sigma}(0{sub 0}, {ital n}=0). The three upper states of these are found to be strongly mixed by anisotropy and Coriolis effects. A simultaneous least squares fit of all transitions has yielded vibrational frequencies, rotational and centrifugal distortion constants, and a Coriolis parameter as well as quadrupole hyperfine coupling constants for the upper states. An effective angular potential energy surface for Ar--NH{sub 3} in its lowest stretching state has been determined from these data, after explicitly accounting for the effects of bend stretch interactions. Features of the surface include a global minimum at the near T-shaped configuration ({theta}=90{degree}), a 30 cm{sup {minus}1} to 60 cm{sup {minus}1} barrier to rotation at {theta}=180{degree} (or 0{degree}), and a very low barrier or possibly a secondary minimum at {theta}=0{degree} (or 180{degree}). Both attractive and repulsive interactions are shown to contribute significantly to the anisotropic forces in the complex. Comparison with {ital ab} {ital initio} calculations are presented.},
doi = {10.1063/1.461430},
url = {https://www.osti.gov/biblio/5467385}, journal = {Journal of Chemical Physics; (USA)},
issn = {0021-9606},
number = ,
volume = 95:1,
place = {United States},
year = {1991},
month = {7}
}